Contaminated evidence can be brought in by witnesses, suspects, victims, emergency responders, fire fighters, police officers and investigators . Juries expect to see forensic evidence before they render a verdict based on that evidence.
What if the evidence is contaminated?
As the crime scene examiner travels from one scene to another they run the risk of transferring hairs, fibers, and biological fluid from other scenes to the new crime scene . This contamination can be easily controlled if crime scene personnel decontaminate their equipment before and after every crime scene.
Why is it important for evidence to not be contaminated?
Because very small DNA samples can be used as evidence , investigators and laboratory personnel must be extremely careful about contamination issues when identifying, collecting, and preserving samples. If contamination occurs, the evidence might never make it to the courtroom.
What are the concerns of evidence contamination How can you protect against this issue?
- Wear gloves. ...
- Use disposable instruments or clean them thoroughly before and after handling each sample.
- Avoid touching the area where you believe DNA may exist.
- Avoid talking, sneezing, and coughing over evidence.
What is cross-contamination in a crime scene?
Cross-contamination – The unwanted transfer of material between two or more sources of physical evidence . For example, improperly collecting biological evidence such as blood could lead to one sample mixing with another sample and contaminating both.
What is an example of contaminated evidence?
In general, the grater number of personnel at the scene , the more likely it is that the scene/evidence will be contaminated. Scene personnel can deposit hairs, fibers or trace material from their clothing or destroy latent footwear or fingerprints.
What evidence is admissible?
To be admissible in court, the evidence must be relevant (i.e., material and having probative value) and not outweighed by countervailing considerations (e.g., the evidence is unfairly prejudicial, confusing, a waste of time, privileged, or based on hearsay).
What type of evidence is impression evidence?
Impression evidence can be generally defined as objects or materials that have retained the characteristics of other objects or materials through direct contact . Footwear and tire tread impressions are the most common types of impression evidence. Footwear examinations are less common than fingerprint examinations.
What is the golden rule in criminal investigation?
When it comes to crime scenes, the golden rule is “ Do not touch, alter, move, or transfer any object at the crime scene unless it is properly marked, measured, sketched and/or photographed .” This rule is to be followed every day, in every scene.
What is considered physical evidence?
Physical evidence can be any object or material relevant in a crime . It can be any tangible thing, large or small. This is also called real evidence.
What are the seven steps of a crime scene investigation?
- Identify Scene Dimensions. Locate the focal point of the scene.
- Establish Security. Tape around the perimeter.
- Create a Plan & Communicate. ...
- Conduct Primary Survey. ...
- Document and Process Scene.
- Conduct Secondary Survey.
- Record and Preserve Evidence.
How are DNA samples collected?
In an instance where the crime scene offers a clear source of DNA (blood, urine, saliva, and samples on steering wheels, etc.), the sample can be collected using a swab . ... Place the tip of the swab on the surface, rotating slightly to allow any DNA to absorb into the fibers.
Can you destroy DNA?
Environmental factors, such as heat and humidity , can also accelerate the degradation of DNA. For example, wet or moist evidence that is packaged in plastic will provide a growth environment for bacteria that can destroy DNA evidence.
What is transfer evidence?
Transfer evidence is defined as any evidential substance or particle such as blood , fluids , hairs, fibers , paint, and skin that is exchanged between an assailant and the victim or the scene of the crime . Such evidence can transfer either from the criminal to the victim or from the victim to the criminal.
What is impression evidence?
Impression evidence is created when two objects come in contact with enough force to cause an “impression .” Typically impression evidence is either two-dimensional — such as a fingerprint — or three-dimensional — such as the marks on a bullet caused by the barrel of a firearm.
What is another word for crime scene investigation?
Crime scene investigators (CSIs) go by many names, including evidence technician , crime scene technician, forensic investigator, crime scene analyst, criminalistics
